N-terminal residues are crucial for quaternary structure and active site conformation for the phosphoserine aminotransferase from enteric human parasite E. histolytica
| Autor: | Rohit Kumar Singh, Samudrala Gourinath, Priya Tomar, Sudhaker Dharavath, Sudhir Kumar |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Models
Molecular Stereochemistry 02 engineering and technology Biochemistry Serine 03 medical and health sciences chemistry.chemical_compound Chlorides Structural Biology Catalytic Domain Humans Transferase Amino Acid Sequence Phosphoserine Aminotransferase Protein Structure Quaternary Molecular Biology Transaminases 030304 developmental biology chemistry.chemical_classification 0303 health sciences biology Entamoeba histolytica Active site General Medicine 021001 nanoscience & nanotechnology Amino acid Kinetics Enzyme chemistry Phosphoserine Mutation biology.protein Protein quaternary structure 0210 nano-technology Sequence Analysis |
| Zdroj: | International Journal of Biological Macromolecules. 132:1012-1023 |
| ISSN: | 0141-8130 |
| Popis: | Phosphoserine aminotransferase (PSAT) is a pyridoxal-5′phosphate (PLP)-dependent enzyme that catalyzes the second reversible step in the phosphoserine biosynthetic pathway producing serine. The crystal structure of E. histolytica PSAT (EhPSAT) complexed with PLP was elucidated at 3.0 A resolution and the structures of its mutants, EhPSAT_Δ45 and EhPSAT_Δ4, at 1.8 and 2.4 A resolution respectively. Deletion of 45 N-terminal residues (EhPSAT_Δ45) resulted in an inactive protein, the structure showed a dimeric arrangement drastically different from that of the wild-type protein, with the two monomers translated and rotated by almost 180° with respect to each other; causing a rearrangement of the active site to which PLP was unable to bind. Deletion of first N-terminal 15 (EhPSAT_Δ15) and four 11th to 14th residues (EhPSAT_Δ4) yielded up to 98% and 90% decrease in the activity respectively. Absence of aldimine linkage between PLP-Lys in the crystal structure of EhPSAT_Δ4 mutant explains for such decrease in activity and describes the importance of these N-terminal residues. Furthermore, a halide-binding site was found in close proximity to the active site. A stretch of six amino acids (146–NNTIYG–151) only conserved in the Entamoeba genus, contributes to halide binding may explain that the halide inhibition could be specific to Entamoeba. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect